Stokes et al. (2014) studied the neurotoxin tetrodotoxin (TTX) in flatworms. The between-plots factor was flatworm species (fixed with two groups: Bipalium adventitium and Bipalium kewense) with individual flatworms (plots) nested within species. The within-plots factor was body segment (fixed with three groups: head, anterior body, posterior body) and each segment represented a “sub-plot”. The response variable was the TTX concentration of tissue adjusted for weight. The main research questions were about the fixed effects of species, body segment and their interaction on TTX concentration, but the analyses also provide information about the variances associated with the random effects of individual within species and the random interaction between individuals within species and body segment.
Bipalium advenitium. Sanjay Acharya, CC BY 4.0, via Wikimedia Commons